The findings suggest that exercise, particularly when tailored to an individual's needs and performed at home, may help Alzheimer's patients maintain their independence and delay the move to a nursing home.

"This is an important study," said Dr. Kostos Lyketsos, director of the Johns Hopkins Memory and Alzheimer's Treatment Center, in Baltimore. "If we could ever deliver exercise for people with dementia in their homes, I think we could accomplish very substantial benefits for patients and reduce costs, which is a very big deal ... in health care these days." Lyketsos was not involved in the new research.

Mental changes are the first wrenching signs of Alzheimer's disease, and they often are the symptoms that get the most attention. But physical declines are also a part the disease. Over time, muscles become stiff and uncoordinated, or may start to tremor. Alzheimer's patients may lose the ability to brush their teeth, climb stairs, and dress, feed and bathe themselves.

"These people are at very high risk of disability. That's one of the reasons they end up in institutional care," said study author Dr. Kaisu Pitkala, a general practitioner at the University of Helsinki. "They need so much help that their caregivers often get very tired, and after a few years they will end up in institutional care, which is very expensive and often not the wish of the patients nor the caregivers."

For the study, published online April 15 in the journal JAMA Internal Medicine, the researchers chose more than 200 patients with moderate to severe Alzheimer's disease who were living at home with a caregiver and showing signs of physical decline. The patients were randomly assigned to one of three groups: home exercise, group exercise at a day care center, or a control group that got usual care through the Finnish national health care system.

Those in the home-exercise group got visits from a physical therapist for one hour twice a week. The physical therapists specialized in dementia care, and they tailored these sessions to each patient's problems with function and mobility.

Patients in the group-exercise classes traveled to an adult care center twice a week, where two physical therapists guided them through exercises to improve endurance, balance, strength and mental function.

The patients in the usual-care group were followed by the study nurses and were given advice on nutrition and exercise.

After one year, all the groups saw declines in physical function, but the groups that exercised regularly fared better than those who got usual care. Those in the home-exercise group did the best. Their physical function declined about half as much as that of the control group. Importantly, they also had half as many falls as those who got usual care.

Group exercisers showed some signs of better health -- their strength improved over the course of the year -- but those results were not statistically significant. And although the study found an association between exercise and better health among Alzheimer's patients, it didn't prove a cause-and-effect relationship.

The researchers think one reason the group exercisers didn't see bigger benefits was because they were more likely to skip their sessions than those who exercised at home.

"When the taxi came to the person's home to take them to the group-based exercise, they could say often, 'Today I'm tired; I'm not coming,'" Pitkala said. "When there's a person coming to your home and telling you, 'Let's do a little bit today,' it's much easier to say yes than it is to go outside your home."

During the year they exercised, patients in the home group had fewer hospital admissions and about half as many falls as those in the control group. The money they saved on medical bills more than offset the cost of regular private sessions with a physical therapist. The average annual cost of caring for a patient in the home-exercise group was about $25,000, but it was about $34,000 for patients who received only usual care. The annual cost for group-exercise patients was even lower, at about $22,000.

Another expert who was not involved in the study praised the research and said it offered a practical blueprint to improve the lives of patients and families affected by Alzheimer's disease.

"If you can do something that can improve their physical functioning and mobility and help them stay home and not actually cost anything -- or be cost neutral -- I think you can make a huge potential impact on a family's quality of life," said Dr. James Galvin, a professor of neurology and psychiatry at NYU Langone School of Medicine, in New York City.